1.口算。
$\frac{7}{24}÷\frac{7}{8}=$
$15×\frac{2}{3}=$
$\frac{2}{3}-\frac{1}{4}=$
$\frac{3}{5}×\frac{1}{3}÷\frac{3}{5}×\frac{1}{3}=$
$\frac{3}{4}+\frac{1}{8}=$
$16÷\frac{4}{7}=$
$\frac{5}{6}×\frac{6}{7}=$
$\frac{2}{9}×\frac{2}{3}+\frac{1}{3}×\frac{2}{9}=$

$\frac{7}{24}÷\frac{7}{8}=\frac{1}{3}$
$15×\frac{2}{3}=10$
$\frac{2}{3}-\frac{1}{4}=\frac{5}{12}$
$\frac{3}{5}×\frac{1}{3}÷\frac{3}{5}×\frac{1}{3}=\frac{1}{9}$
$\frac{3}{4}+\frac{1}{8}=\frac{7}{8}$
$16÷\frac{4}{7}=28$
$\frac{5}{6}×\frac{6}{7}=\frac{5}{7}$
$\frac{2}{9}×\frac{2}{3}+\frac{1}{3}×\frac{2}{9}=\frac{2}{9}$

(1)$\frac{5}{6}+\frac{5}{12}+\frac{5}{12}+\frac{5}{6}=\frac{5}{6}×(\ )=\frac{5}{12}×(\ )=(\ )$。

$\frac{5}{6}+\frac{5}{12}+\frac{5}{12}+\frac{5}{6}=\frac{5}{6}×(3)=\frac{5}{12}×(6)=(\frac{5}{2})$

(2) $\frac{3}{5}\mathrm{km}=(\quad)\mathrm{m}$ $\quad$ $\frac{3}{4}\mathrm{时}=(\quad)\mathrm{分}$ $\quad$ $\frac{1}{8}\mathrm{m}^3=(\quad)\mathrm{dm}^3$

$\frac{3}{5}×1000=600$
$\frac{3}{4}×60=45$
$\frac{1}{8}×1000=125$
$\frac{3}{5}\mathrm{km}=(600)\mathrm{m}$
$\frac{3}{4}\mathrm{时}=(45)\mathrm{分}$
$\frac{1}{8}\mathrm{m}^3=(125)\mathrm{dm}^3$

(3)20 kg的$\frac{4}{5}$是()kg，()m的$\frac{2}{5}$是20 m。

16；50

$20×\frac{4}{5}=16(\mathrm{kg})$
$20÷\frac{2}{5}=50(\mathrm{m})$

(4)分母是3的所有真分数的积是()。

$\frac{2}{9}$

$\frac{1}{3} × \frac{2}{3} = \frac{2}{9}$

(5)在○里填“＞”“＜”或“=”。
$11÷\frac{4}{5}$ ○ $11$
$\frac{7}{24}×\frac{3}{4}$ ○ $\frac{3}{4}$
$\frac{8}{9}×50$ ○ $\frac{8}{9}÷\frac{1}{50}$
$17÷\frac{4}{5}$ $17$
$\frac{11}{10}×\frac{6}{5}$ ○ $\frac{11}{10}$
$\frac{2}{3}×0.5$ ○ $\frac{2}{3}÷2$

$11÷\frac{4}{5}$ ＞ $11$
$\frac{7}{24}×\frac{3}{4}$ ＜ $\frac{3}{4}$
$\frac{8}{9}×50$ = $\frac{8}{9}÷\frac{1}{50}$
$17÷\frac{4}{5}$ ＞ $17$
$\frac{11}{10}×\frac{6}{5}$ ＞ $\frac{11}{10}$
$\frac{2}{3}×0.5$ = $\frac{2}{3}÷2$

(6)根据下图中的数量关系填空。

$(\ )×\frac{3}{5}=(\ )$
$(\ )÷\frac{3}{5}=(\ )$

$(B)×\frac{3}{5}=(A)$
$(A)÷\frac{3}{5}=(B)$

3.脱式计算。
$(\frac{1}{6}+\frac{5}{9})×18$
$\frac{4}{11}×\frac{1}{5}+\frac{7}{11}÷5$
$\frac{2}{19}×\frac{5}{7}×(19×14)$
$\frac{9}{40}÷\frac{3}{10}×\frac{7}{10}$
$\frac{9}{17}÷[\frac{9}{19}×(\frac{3}{5}+\frac{2}{3})]$
$\frac{3}{8}÷[\frac{7}{8}-(\frac{2}{5}+\frac{1}{4})]$

$(\frac{1}{6}+\frac{5}{9})×18$
$=\frac{1}{6}×18+\frac{5}{9}×18$
$=3+10$
$=13$
$\frac{4}{11}×\frac{1}{5}+\frac{7}{11}÷5$
$=\frac{4}{11}×\frac{1}{5}+\frac{7}{11}×\frac{1}{5}$
$=(\frac{4}{11}+\frac{7}{11})×\frac{1}{5}$
$=1×\frac{1}{5}$
$=\frac{1}{5}$
$\frac{2}{19}×\frac{5}{7}×(19×14)$
$=(\frac{2}{19}×19)×(\frac{5}{7}×14)$
$=2×10$
$=20$
$\frac{9}{40}÷\frac{3}{10}×\frac{7}{10}$
$=\frac{9}{40}×\frac{10}{3}×\frac{7}{10}$
$=\frac{3}{4}×\frac{7}{10}$
$=\frac{21}{40}$
$\frac{9}{17}÷[\frac{9}{19}×(\frac{3}{5}+\frac{2}{3})]$
$=\frac{9}{17}÷[\frac{9}{19}×\frac{19}{15}]$
$=\frac{9}{17}÷\frac{3}{5}$
$=\frac{15}{17}$
$\frac{3}{8}÷[\frac{7}{8}-(\frac{2}{5}+\frac{1}{4})]$
$=\frac{3}{8}÷[\frac{7}{8}-\frac{13}{20}]$
$=\frac{3}{8}÷\frac{9}{40}$
$=\frac{5}{3}$